Wisteria isn’t widely grown on this side of the mountains. A lot of people say they just can’t get them to grow or bloom. They should. They are hardy here and really don’t have many peculiar growing needs to make them difficult.
Just ask Peggy Seier. She recently sent me some gorgeous photos of her wisteria in full bloom hanging off her north Spokane deck. She doesn’t fuss over it, just gives it a good pruning every year and it blooms its heart out. With our mild winter, she said the plant did exceptionally well this year
Wisteria need two things: space and lots of sun. An established vine can grow 15 to 20 feet a year and create a very heavy crown. Therefore you’ll need a sturdy trellis, wall or deck structure to anchor it.
Most commercially available trellises are too lightweight. When I was growing up, my dad had to climb on the roof a couple of times a summer to keep ours from taking over the roof, the dogwood and the TV antenna.
Make sure there are at least six hours a day of sun not only where you are planting it but also where it is likely to run. The main part of Seier’s plant faces south and east so it gets close to 12 hours of sun a day. Lack of sun is usually the main reason they don’t bloom.
Wisteria likes a loamy soil with a pH of 6 to 7. This may mean adding some peat moss or granulated sulfur to the soil to lower the pH. If you are in sand, add compost along with the peat moss. Wisteria needs an even supply of moisture to keep the vines hydrated. Think about giving the plant its own sprinkler head and keeping other plants out of the root area to reduce competition for water. Otherwise wisteria needs only a dressing of compost in the spring. Don’t give them fertilizer. Even a little extra nitrogen can create a lot of growth at the expense of flowers.
The Chinese and Japanese varieties are the most commonly available. The main difference between them is the color of their flower and how many of the flowers open at one time. The Chinese wisteria (Wisteria sinensis) produces blue, purple and white flowers that open all at once. The Japanese variety (W. floribunda) blooms in blue, pink, white, purple or violet flowers that open from the base of the flower first for a more sustained show. Japanese wisteria is hardy to USDA Zone 4 while the Chinese variety is hardy to Zone 5. (We live in Zone 5.)
Buy grafted plants or plants that are grown from cuttings. A grafted or cutting grown plant may take five years to begin blooming while seed-grown plants may take 10 or more years. Wisteria needs to be cut back hard just after blooming in the early summer to stimulate bud production and keep the plant under control.